This invention relates to a package suitable for use in cooking, in a microwave oven, food items which require browning or crispening, and suitable for serving such food items, and a process for packaging such food items by skin packaging processes.
Microwave ovens have become widespread in recent years, and have provided a way to rapidly and conveniently cook many types of foods. Certain foods, however, have proven difficult to heat satisfactorily in a microwave oven. Since microwaves penetrate to the interior of the food and heat from the inside, they tend to drive moisture to the relatively cooler surface of the food, where it may condense. While this phenomenon is not particularly troublesome for many foods, for certain foods it presents serious problems. This is a particular problem for foods such as egg rolls, french fried potatoes, etc., which, when traditionally prepared, have a hot moist interior and a hot, crispy exterior. However, when such food items are cooked in a microwave oven, the result is normally a soggy, unappetizing mass, with no surface crispness at all. To alleviate this problem and aid the browning and crispening of the surface of a cooked food item, there have been developed a number of packaging materials specially adapted for use in microwave cooking. Many such known packaging materials incorporate a microwave susceptor material, i.e., a material capable of absorbing the electric or magnetic portion of the microwave field energy to convert that energy to heat.
U.S. Pat. No. 4,276,420, to Brastad, discloses a packaging material which is a plastic film or other dielectric substrate having a thin semiconducting metallic coating. A food item is wrapped in the coated film so that the film conforms to a substantial surface portion of the food item. On exposure to microwave energy, the film converts some of that energy into heat which is transmitted directly to the surface portion by conduction so that a browning and/or crispening is achieved.
Copending U.S. Pat. Ser. No. 037,987, filed Apr. 13, 1987, now U.S. Pat. No. 4,892,782, Fisher and Huang, discloses composite materials comprising drapable, liquid permeable, woven or non-woven, fibrous dielectric substrates. These substrates, or fibers of these substrates, are coated and/or imbibed with one or more susceptor materials. The composite materials of this application are capable of conforming substantially to the shape of the food item to be browned or crispened. The susceptor material converts a portion of the incident microwave radiation to heat, which imparts rapid browning and/or crispening to the exterior surface of the wrapped food item. The composite material also allows moisture evolved during heating of the food item to readily escape as vapor, thereby aiding and hastening browning and crispening of the food surface.
U.S. application No. 065,982, filed Jun. 24, 1987, now abandoned, discloses a process for skin packaging food, applying a flexible lid to food contained within a tray. The lid is formed from a sheet of plastic which is conformed to the tray and its contents by applying vacuum while the sheet is in a hot, pliable state. The tray is supplied with vents in its walls to permit efficient evacuation of air from the tray.
An object of this invention is to provide a microwave active packaging system for food items.. which permits the food item to be heated or cooked in a microwave oven, while simultaneously providing a browned, crisp surface. Another object of this invention is to provide a package which is convenient to use, and which maintains good contact between the microwave active packaging material and the food item during the course of the heating, and which incorporates a tray which can be used for serving of the food items. Other objects of the invention will become apparent from the discussion which follows.